1. Field
The present disclosure relates generally to processing images and, in particular, to identifying objects in images. Still more particularly, the present disclosure relates to a method and apparatus for identifying target objects in images using contextual information in the images.
2. Background
Target recognition is the identification of one or more target objects in a number of images. The target objects to be identified may include, for example, without limitation, people, vehicles, buildings, structures, geographic features, and/or other types of objects. Target recognition may be used when performing various types of missions. These missions may include, for example, without limitation, surveillance, reconnaissance, weapons deployment, cargo drops, and/or other suitable types of missions.
Oftentimes, radar imaging is used to generate the images used in these types of missions. Synthetic aperture radar (SAR) imaging is a form of radar imaging in which an antenna may be mounted to a mobile platform. Typically, the mobile platform is an aerospace platform. An aerospace platform may be, for example, without limitation, an aircraft, an unmanned aerial vehicle, a helicopter, a missile, a satellite, a space shuttle, or some other suitable type of aerospace platform.
With synthetic aperture radar imaging, the mobile platform carrying a synthetic aperture radar system moves along a path. As the mobile platform moves along the path, an antenna in the synthetic aperture radar system sends pulses of electromagnetic radiation. This electromagnetic radiation is in the form of electromagnetic waves, which are also referred to as electromagnetic signals. These electromagnetic signals may have wavelengths, for example, from about 10 millimeters to about one meter.
The electromagnetic signals are directed at an area. The area may be, for example, an area of terrain, a block in a neighborhood, a section of a forest, a portion of a city, a plant, a bridge, or some other suitable type of area.
When these electromagnetic signals encounter a surface of the area, at least a portion of the electromagnetic signals is reflected off of the surface. The electromagnetic waves that are reflected off the surface may be referred to as backscatter, scattered electromagnetic waves, scattered electromagnetic signals, echo waves, or echoes.
As the mobile platform moves along the path over the area, the antenna detects the electromagnetic signals reflected off of the surface in response to the pulses sent by the antenna. The electromagnetic signals received at the antenna as the antenna moves along the path are processed to form an image of the area.
Additionally, synthetic aperture radar imaging may be implemented as inverse synthetic aperture radar imaging. This type of imaging is performed using a stationary antenna or an antenna mounted to a stationary platform. An image is generated for moving objects in the area observed over time.
With currently-available systems for target recognition using the number of images generated using synthetic aperture radar imaging, false identifications of objects may occur more often than desired. Corrective actions may need to be taken when false identifications occur. As a result, additional processing may occur to verify that the objects that have been identified are the target objects. Further, the time needed to recognize objects may be important when using that information to control the mobile platform or perform other actions that are time sensitive. The time needed to perform target recognition using currently-available systems may be greater than desired.
Therefore, it would be advantageous to have a method and apparatus that takes into account at least some of the issues discussed above, as well as possibly other issues.